Extensible scaffold

ABSTRACT

The invention relates to an extensible scaffold of the type comprising telescoped scaffold elements movable between an extended and a retracted position and interconnected by means of ropes, chains, wires, or similar flexible members. According to the invention the scaffold elements may have hollow columns or tubes arranged vertically at the periphery or outline of each element. Preferably, the elements have a polygonal outline or cross-section, and the said columns or tubes are arranged at the vertices or corners thereof. The flexible elements or wires extend at least partly through the hollow columns or tubes and are thereby protected against damaging. Preferably, the flexible members or wires are wound by a winch device comprising a number of pulleys mounted on a common winding shaft and each defining a narrow channel or groove for receiving and accommodating an associated flexible member in a spirally wound condition in order to obtain identical winding rates for all of the flexible members.

United States Patent Rasmussen 1 Oct. 22, 1974 1 EXTENSIBLESCAFFOILD [76] Inventor: Knud Rasmussen, Koge, Brogade [30] Foreign Application Priority Data Nov. 17, 1971 Denmark 5639/71 [52] US. Cl. 52/645, 182/141 [51] Int. Cl. E04g 1/18 [58] Field of Search 182/63, 141, 148, 178; 52/645 [56] References Cited UNlTED STATES PATENTS 3,000,473 M1961 Reynolds 182/63 3,017,968 1/1962 McMahon 182/141 Primary Examiner-Reinaldo P. Machado Attorney, Agent, or FirmDennison, Dennison, Townshend & Meserole [5 7] ABSTRACT The invention relates to an extensible scaffold of the type comprising telescoped scaffold elements movable between an extended and a retracted position and interconnected by means of ropes, chains, wires, or similar flexible members. According to the invention the "scaffold elements may have hollow columns or tubes arranged vertically at the periphery or outline of each element. Preferably, the elements have a polygonal outline or cross-section, and the said columns or tubes are arranged at the vertices or corners thereof. The flexible elements or wires extend at least partly through the hollow columns or tubes and are thereby protected against damaging. Preferably, the flexible members or wires are wound by a winch device comprising a number of pulleys mounted on a common winding shaft and each defining a narrow channel or groove for receiving and accommodating an associated flexible member in a spirally wound condition in order to obtain identical winding rates for all of the flexible members.

5 Claims, 9 Drawing Figures PATENT En 001221914 sum 1 or a PAIENTEDHBTZZW' 3.842.568-

' SHEEI NF 3 EXTENSIBLE SCAFFOLD BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extensible scaffold of the type comprising a number of scaffold elements telescopicly movable between a retracted and an extended position and interconnected by ropes or wires passing over pulleys or similar guiding members arranged at the ends of said elements.

2. Description of the Prior Art Such scaffold which may be provided with an upper platform for supporting working persons, or be adapted to serve any other purpose of support has the advantage that the scaffold elements may be displaced telescopicly in relation to each other so that the elements may be moved to a retracted position in which the scaffold is rather compact and may easily be transported or stored. When desired, the scaffold elements may easily be telescopicly moved to a totally or partly extended position, for example by means of pressure fluid cylinders or by means of a manually or motor operated winch for the ropes or wires interconnecting the scaffold elements. Thereafter the scaffold elements may be locked together in the desired relative positions by means of suitable locking members. It is important to have a suitable relation between the effective lower supporting surface and the total height of the extended scaffold in order to obtain an acceptable stability of the scaffold, and it is also important that each scaffold element is being supported in a stable manner when elevating the same to its extended position.

In the known scaffolds of the type described above the pulleys or guiding members at the lower end of each scaffold element are arranged in such a manner that the effective supporting surface defined by the elevating forces applied to said element through the ropes or wires is substantially smaller than the cross-section of said scaffold element, because in the known scaffolds consisting of box-shaped elements the pulleys or guiding members are normally arranged in intermediate positions at the longest side of the box-shaped scaffold element. Therefore, it is necessary to have a substantial length of the lower end portion of each scaffold element surrounded by and guided in the adjacent outer element even in the fully extended condition of the scaffold. Furthermore, in the known scaffolds the elevating ropes or wires are liable to become damaged, partly because the exposed wire sections may interfere with each other or with other scaffold parts when the scaffold elements are moved to their extended or retracted position, and partly because the ropes or wires may easily be damaged during use of the scaffold, for example, by droplets of molten metal or slags when welding operations or blow pipe operations are performed by persons standing on the scaffold platform, or by drops of acid, when persons standing on the scaffold platform are washing walls with acid. There is also a certain risk that the exposed ropes or wires may become damaged by interfering with protruding parts, for example of machines and trees when the extended scaffold is being moved from one position to another. Furthermore, tools, materials, and other items falling from the working platform of the scaffold, twigs and similar foreign bodies may be caught by the wires and thus be moved over the pulleys and give rise to troubles when the scaffold is later being brought into its retracted condition.

SUMMARY OF THE INVENTION The scaffold according to the invention comprises a number of telescoped scaffold elements movable between an extended and a retracted position, each element including substantially vertically arranged hollow columns or tubes, a plurality of elongated flexible connecting members extending through said columns or tubes for interconnecting said scaffold elements, and guiding means arranged at the end of said columns or tubes for guiding said flexible connecting members when said scaffold elements are moved in relation to each other. The said columns or tubes which preferably constitute supporting parts or struts in the scaffold elements protect all or substantially all parts of the flexible connecting members or wires against damaging when the scaffold is in its extended or elevated condition, and furthermore, an effective separation of the wire sections arranged within the columns or tubes and the wire sections positioned between the telescoped elements in the retracted scaffold condition is obtained.

The scaffold elements may have a substantial polygonal cross-section, and the said hollow columns or tubes and the associated pulleys or guiding members may then according to the invention preferably be arranged at the vertices increase polygonal cross-section or at the comers of the scaffold elements. The effective supporting surface defined by the elevating forces applied to the pulleys arranged at the lower end of each scaffold element will then have a size of substantially the same order as the cross-section of the respective scaffold elements. It is thereby obtained that the elevating wires will support each scaffold element in such a stable manner that in the fully extended condition of the scaffold the elements thereof need not or need only to a very slight extent engage with each other or guide each other. The increases in useful height of each scaffold element obtained thereby renders it possible for a certain maximum height of the fully extended scaffold to obtain as well a weight reduction as either a reduced number of scaffold elements, or a reduced height of each single element. In the last mentioned case the height of the fully retracted scaffold is reduced whereby the scaffold may more easily be transported and moved through gate openings and other passages with restricted height.

As mentioned previously the elevation or extension of the scaffold elements may be obtained by means of either pressure fluid cylinders or a manually or motor operated winch. In the last mentioned case the scaffold may be of the type comprising a winding shaft common to all of the ropes or wires. Despite of that measure a certain rotational movement of the winding shaft does not necessarily shorten or prolong the non-wound part of each rope or wire to the same extent, because during winding the wires may arrange themselves differently around the shaft or a drum mounted thereon. This is rather disadvantageous, especially when the scaffold elements are not being guided in relation to each other during elevation or extension, because the elements may then deviate from their vertical The invention will now be described more in detail with a reference to the drawing showing an embodiment of the scaffold according to the invention, and wherein FIG. 1 shows a plan view of the scaffold,

FIG. 2 shows a side view of the scaffold in its retracted condition,

FIGS. 3 and 4 show in an enlarged scale a side view and a plan view, respectively, of a corner of the retracted scaffold for illustrating the path of an elevating wire,

FIG. 5 shows a side view and partial sectional view of two telescoped scaffold elements locked together,

FIG. 6 shows a side view and partial sectional view of two scaffold elements in an extended condition and locked together,

FIG. 7 shows a plan view and partial sectional view of parts of the elements shown in FIG. 5, and

FIGS. 8 and 9 show a plan view and a side view, respectively, of a clamping device for locking two corner columns or tubes in adjacent scaffold elements together.

DESCRIPTION OF THE PREFERRED EMBODIMENT.

The scaffold illustrated in the drawing consists mainly of telescoped box-shaped scaffold elements 1, 2, 3, and 4, each comprising hollow comer columns or tubes 15. The scaffold elements may be telescopicly elevated or extended in relation to each other by means of four wires or ropes 13 each arranged in a corner of the scaffold and passed over pulleys l4 rotatably mounted at each end of each column 15 in the elements 2 4, said pulleys 14 being rotated substantially in the diagonal plans of each scaffold element. The pulleys 14 are partly enclosed by shielding members 17 (FIG. 3) mounted on the respective scaffold element. As best shown in FIG. 3 each of the wires is passed through the hollow corner columns 15 and in the retracted condition of the scaffold also through the spaces defined between adjacent corner columns in a diagonal plan. A winding shaft 7 having a small torsional resiliency is common to all of the wires and provided with two double winch pulleys 8 each defining a narrow groove or channel 18 extending in a radial plane. Each of the four wires 13 has its free end connected to one of the pulleys 8 in one of the grooves 18 and each groove has a width corresponding substantially to the thickness or outer diameter of the wires so that each of the wires will be spirally wound in a single radial plane when the winding shaft 7 is rotated whereby a completely uniform winding of the four wires is secured. The other ends 19 of the wires are fastened to the four lower corners of the innermost scaffold element 1 as shown in FIG. 3. The winding shaft 7 with the winch pulleys 8 is rotatably mounted at the lower part of the scaffold as shown in FIGS. 1 and 2 and may be manually rotated by means of a-chain 5 and associated sprockets, one of which may be rotated by means of a crank handle 6. Thus, the telescoped scaffold elements 1 4 may be elevated or retracted in relation to each other by operating the crank handle 6. The innermost scaffold element 1 is higher than the others and provided with a working platform 16 at the top. The outermost scaffold element 4 may be provided with wheels indicated at 20 for facilitating transport of the scaffold.

Each of the scaffold elements 1 3 may at each lower corner be provided with a welded bracket 9, and each of the scaffold elements 2 4 may at its upper and lower corners be provided with a vertical conical stud 10 each having a slot for receiving a wedge member 11. Each pair of these studs are vertically aligned and oppositely directed and may be passed through corresponding holes in the brackets 9 on the adjacent scaffold element. The scaffold elements 1 4 may be locked together as well in their fully retracted position FIGS. 5 and 7) as in their fully extended position (FIG. 6) by inserting the wedge members 11 into the slots in the stud 10 when these are in engagement with the associated brackets 9.

In FIGS. 1 and 2 the scaffold is shown in its fully retracted position, and the elements are locked together by means of the wedge members 11 as just described above. When the scaffold is to be extended the wedge members 11 locking the scaffold element 1 to the element 2 is first removed, and the winding shaft 7 as well as the winch pulleys 8 mounted thereon are thereafter rotated by means of the crank handle 6. Thereby the element 1 is elevated. This elevating movement may be stopped in any position, and the element 1 may be fastened to the element 2 by means of clamping devices 12 of the type illustrated in FIGS. 8 and 9, the adjacent corner columns 15 of the said elements being clamped together by means of these clamping devices. If, however, the element 1 is elevated to its fully extended position it may be locked by means of the brackets 9 and the studs 10 which are in engagement in that position and may be locked together by means of wedge members 11. Now the wedge members locking the elements 2 and 3 together are removed, and the element 2 may then be elevated by continuous rotating of the winding shaft 7.'Just like the element 1, the element 2 may be fastened either in its fully extended position by means of the locking members 9 11, or be clamped in an intermediate position by means of clamping devices 12. The scaffold elements 3 and 4 may successively be fully or partly elevated in a similar manner.

Partly due to the fact that each of the elements 1 3 are being supported by the wires 13 right at their corners, and partly due to the uniform winding of the wires or ropes obtained by the winch pulleys 8 mounted on the winding shaft 7 it is not necessary to have any of the scaffold elements 1 3 guided within and by the surrounding adjacent scaffold elements. For that reason it is not necessary to produce the scaffold elements with close tolerances, and furthermore the risk that the scaffold elements become jammed or wedged due to deviation from their vertical position when they are being moved in relation to each other is being substantially reduced.

I claim:

1. A telescoping scaffold comprising a. a number of scaffold sections including a base section, at least one intermediate section, and a top section, each section comprising a number of upright tubular comer posts, and each intermediate and top section being telescopically arranged within a lower adjacent section with a loose fit so as to provide a transverse clearance between adjacent corner posts of such adjacent sections,

b. pulley means mounted at the upper end of said base section and at the lower and upper ends of said intermediate section or sections,

c. lift cable means extending about said pulley means and through said corner posts and connected to the lower end of said upper section,

d. means mounted on said base section and connected to the lower ends of said cable means for manually pulling each of said cable means uniformly about said pulley means thereby to move one or more of said top and intermediate sections upwardly to extend the scaffold, and

e. means for selectively and releasably locking adjacent sections together in various mutual positions.

being adapted to receive and accommodate an associated cable means in a spirally wound condition when the said winding shaft is being rotated, and a crank handle for manually rotating said winding shaft.

4. A scaffold according to claim 1, wherein said locking means comprises clamping devices for embracing and clamping pairs of corner posts in adjacent sections.

5. A scaffold according to claim 1, wherein said locking means comprises vertically aligned and oppositely directed upper and lower studs of at least one of said sections, and a bracket on an adjacent upper section, said bracket having an opening for receiving said upper and lower studs in a fully extended and retracted position for said adjacent upper section, respectively, each of said studs having a transverse slot for receiving a wedge-shaped member so as to lock said bracket to said stud when received in said opening in the bracket. =l 

1. A telescoping scaffold comprising a. a number of scaffold sections including a base section, at least one intermediate section, and a top section, each section comprising a number of upright tubular corner posts, and each intermediate and top section being telescopically arranged within a lower adjacent section with a loose fit so as to provide a transverse clearance between adjacent corner posts of such adjacent sections, b. pulley means mounted at the upper end of said base section and at the lower and upper ends of said intermediate section or sections, c. lift cable means extending about said pulley means and through said corner posts and connected to the lower end of said upper section, d. means mounted on said base section and connected to the lower ends of said cable means for manually pulling each of said cable means uniformly about said pulley means thereby to move one or more of said top and intermediate sections upwardly to extend the scaffold, and e. means for selectively and releasably locking adjacent sections together in various mutual positions.
 2. A scaffold according to claim 1, wherein said sections are of a lattice-like structure substantially made up by tubes having a circular cross section.
 3. A scaffold according to claim 1, wherein said cable pulling means comprise a rotatable winding shaft having parts defining a number of uniform radially extending annular channels or grooves corresponding to the number of cable means, said channels or grooves having an axial width corresponding to the outer diameter or thickness of the cable means, each said channels being adapted to receive and accommodate an associated cable means in a spirally wound condition when the said winding shaft is being rotated, and a crank handle for manually rotating said winding shaft.
 4. A scaffold according to claim 1, wherein sAid locking means comprises clamping devices for embracing and clamping pairs of corner posts in adjacent sections.
 5. A scaffold according to claim 1, wherein said locking means comprises vertically aligned and oppositely directed upper and lower studs of at least one of said sections, and a bracket on an adjacent upper section, said bracket having an opening for receiving said upper and lower studs in a fully extended and retracted position for said adjacent upper section, respectively, each of said studs having a transverse slot for receiving a wedge-shaped member so as to lock said bracket to said stud when received in said opening in the bracket. 